There's a monkey wrench here,

Most aquatic plants thrive best in sandy, well-ventilated soil, but very few plants grow 'only' in sand.

In any case, there are a few plants that make pretty good hard-bottom indicators.

If you're looking for sandy substrate in a dark bottom bay (covered with humus or detritus)

the 4 plants below are good sand-bottom indicators:

Bulrushes (Scirpus)

Watershield (Brasenia schreberi)

Elodea (Elodea canadensis)

Pennywort (Hydrocotyle umbellata)

Roger

This is exactly what I was hoping for. Thank you!

One can study the different types of grasses located in their favorite fishing waters.

 

What is also important is to know is where two types of grass meet; any wood or other structure under, around or on top of the grass; how fast is the grass going to grow; and last but the most important thing to understand about grass is "where is the grass line in relation to the bank?"

 

When the tide goes out on tidal rivers; when storms approach, arrive and then leave; in the pre and post spawn days; when the water temperatures rise; and where the bait fish are hiding; you have to know where the break lines are situated so you can fish them.

 

Ever see someone in a river or lake way off the bank throwing into open water? They are fishing the underwater grass lines, brush piles, rocks or other structure.  Ever notice a pro bass fisherman fishing around and in front of docks? All are seeking the drop offs, changes in structure, rocks and any grass lines they can note on their electronics.

 

Even if you know the grass lines and the bottom contour it is also important to find the baitfish. You find a grass line with minnows and you have yourself an excellent place to try your skills.

The number of various types of bottom composition is not as wide as one might assume. The overlap of multiple species of vegetation on a single bottom composition is numerous there by making identifying bottom composition rather easy.

The number of various types of bottom composition is not as wide as one might assume. The overlap of multiple species of vegetation on a single bottom composition is numerous there by making identifying bottom composition rather easy.

 

I believe the OP is interested in plant species that can serve as a biomarker for hard substrate

(very wise approach during the bedding season). However, according to nature's master plan,

most plant species are highly adaptable, and may be found growing in a wide variety of soil textures.

Nearly all beneficial plants grow in sandy, well-ventilated soil, but very few plants grow ONLY in sandy soil.

As a result, plant species do a rather poor job of identifying bottom content.

 

Spatterdock is one of the best aquatic plants in central Florida for harboring Florida-strain bass

(it resemble waterlilies, but rather than lying on the surface, about half the pads are held 'above' the water).

I've found lush beds of spatterdock growing in sand, in loam, in clay and in mud.

 

Roger